The present invention relates in general to telecommunication techniques. More particularly, the invention provides a system and method for providing failure protection. Merely by way of example, the invention is described as it applies to optical networks, such as Wavelength Division Multiplex Passive Optical Networks, but it should be recognized that the invention has a broader range of applicability.
Recently, the demand for broadband access operations has increased rapidly. In order to meet the demand for high-bandwidth and high-capacity access, the industry often chooses the optical access communication network. However, the cost for some of the important components of the optical access communication network is relatively high. Thus, the industry is seeking ways to build a cost-effective optical network. Research on Passive Optical Network (PON) technology also has become increasingly popular. For example, the industry has witnessed the emergence of the ATM-based Passive Optical Network (APON), the Broadband Passive Optical Network (BPON), the Passive Optical Network based on Ethernet (EPON), the Gigabit Passive Optical Network (GPON), the Wavelength Division Multiplex Passive Optical Network (WDM-PON), and Optical Code Division Multiple Access Passive Optical Network (OCDMA-PON) and other optical networks.
Generally speaking, the Passive Optical Network is, for example, this type of a system: a service provider's Central Office (CO) and remote nodes are connected through a fiber optic trunk. The remote nodes are located near user locations and connected to Optical Network Terminals (ONTs) of the consumer side through a distributed fiber-optic. Since passive optical components are disposed in the remote nodes, thus, the PON often allows tremendous reduction in administrative levels and maintenance costs.
FIG. 1 is a simplified diagram for a conventional WDM-PON system. As shown in FIG. 1, multiple wavelengths provided by a CO are transmitted to a remote node (RN) through a single fiber optic, each wavelength λi is transmitted to each ONTi through the wavelength division function of the RN, and the corresponding ONT can send uplink data and receive downlink data with the distributed wavelengths.
FIGS. 2(A) and (B) are simplified diagrams showing conventional failure of a laser transmitter and a laser receiver respectively. As shown in FIGS. 2(A) and (B), once a transmitter i or a receiver i fails, the channel i would consequently become unusable. A solution to this problem is to use a protection method.
For example, a conventional protection method uses an optical channel protection (OCP) module for transmission and an OCP module for reception in a WDM system. Hence the transmission system and the reception system each have at least a protection channel in addition to working channels. When one working channel fails, the WDM system sends a changeover request, and in response, the signals are changed over from the assigned working channel to the assigned protection channel. When the working channel failure is repaired, signals of the assigned protection channel are restored back to the working channel.
Hence it is highly desirable to improve techniques for providing failure protection.